Something I was just wondering about... I learnt to never put the volume to the maximum, because the signal may be capped which sounds bad and may potentially damage your speakers. However, I discovered that VLC has a setting that says "enable peak protection", meaning that you can safely put the volume to 100% without fear of capping.

Now that I know about it it makes a lot of sense to me that a decent audio player would offer such a feature. That makes me think that iTunes and QuickTime probably do it too, but without telling the user about it. Could anyone confirm that? Sofar I've been unable to find any conclusive answer on the internet. If I knew for sure that I can safely max out the volume in iTunes I'd find that very convenient.

iTunes/QuickTime don't have "peak protection" because they don't allow you to add gain to a digital signal: at full volume in either iTunes or QuickTime, 0 dBFS from a PCM audio file = 0 dBFS out to the audio driver.

VLC, for some bizarre reason, does allow you to add substantial gain, and thus can easily drive a signal well into digital clipping. Its "peak protection" is basically a real-time normalizer that decreases gain anytime it detects clipping.

As an aside, the DirectShow AC3Filter has had that same feature for quite some time, which works in tandem with its dynamic range compression (DRC).